Mandy and our neighbor dog, Buddy (who seldom goes home) begin every day wrestling like this. I lock Mandy in her pen in the barn around 8 PM, and there she stays for ten hours or so. Often when I go to turn her out in the morning, Buddy is curled up next to the pen, where he's obviously spent the night. If I don't get right outside to turn Mandy loose, Buddy will whine at my back door, begging for freedom for his playmate.
The dogs appear to be chewing one another to bits, but there's never a yelp of pain; they've learned to pull their punches, after a year of this sort of activity, every day.
When my grandpuppy, Dixie, comes to visit, she immediately joins the frolic.
They can go on like this for an hour at a time.